A class-D amplifier in which output stage transistors perform switching operation is increasingly being used as a drive circuit that drives a sound-producing device, such as a piezoelectric element and an electrostatic loudspeaker.
The class-D amplifier includes, as an output device, MOSFETs having a low on-resistance, and causes the MOSFETs to perform switching operation to reduce loss in the output device.
In the class-D amplifier, the loss in the output device is smaller than that in an analog amplifier, and a radiator can be omitted or reduced in size. The class-D amplifier can achieve a small and high-power amplifier, and thus can be used as an amplifier for a mobile terminal.
Output of the output device of the class-D amplifier has a switching waveform, and is thus supplied to a load after a low-pass filter (LPF) eliminates switching carrier components therefrom.